The present invention relates to a contact-type switch that includes a housing and, disposed in the housing, a plunger or push member having a long-stroke configuration, whereby essentially immediately after a shifting out of an outer end position and in a direction that is essentially in the direction of a central axis of the housing, the plunger breaks or opens at least one switch contact that is disposed in the housing, and whereby a specific displacement path or dead travel is carried out by the plunger between the outer end position thereof and the point or position where the switch contact is broken.
A contact-type switch of this general type is known (DE-OS 36 29 650). Contact-type switches of this type are used particularly in the automobile industry and are frequently used as switches for closing a circuit, for example when vehicle doors are opened and as a consequence thereof lights within the passenger space of the vehicle are switched on. As a result of the door constructions that are generally utilized in the modern motor vehicle industry, it is necessary that switches of this type for these purposes carry out considerable switch strokes or travel. Switch-extending constructions to solve such problems are not suitable, since in contact-type switches the stroke or travel of the switch plunger must be determined by the construction of the switch itself, and plunger-extending measures thus offer no solution to this problem.
With the heretofore known contact-type switches, which are installed in a large number of motor vehicles that are available on the market these days, and which switches also basically showed very good switching characteristics in operation, it was found that under conditions of extreme atmospheric moisture in the region where the contact-type switch was disposed on the vehicle door, disruptions in operation could not be completely precluded. The basis for these disruptions in operation is that the plastic that is used for the individual structural elements of the switch, and that is provided with its final shape via an injection molding process, exhibits the tendency to occlude water in a molecular manner in the surface layer of the plastic, resulting, for example, in a radial expansion of the diameter of the switch plunger of the known contact-type switch; this suffices to allow the plunger to become wedged or seized in the switch in its guide or mounting means, which are made of the same material. Although this shortcoming was attempted to be eliminated by enlarging the opening of the entry region of the switch plunger into the housing, so that as a result radial increases in the cross-sectional area no longer resulted in the aforementioned drawbacks, none the less the result of this measure was that since a satisfactory guidance of the switch plunger in the housing could then no longer be ensured, shortcomings relative to the switching reliability occurred that under all circumstances had to be avoided, so that this course for eliminating the original shortcoming could not be taken.
It is therefore an object of the present invention to provide a contact-type switch that on the one hand is an economical, mass produced product that can be installed in motor vehicles and can carry out its switching functions in a reliable manner over a long operational time span, and that on the other hand can continuously carry out its switching functions as designed even under extreme conditions of atmospheric moisture.